Optical disk apparatus and computer readable recording medium storing program

ABSTRACT

An optical disk apparatus for forming an image on an optical disk according to dot data which defines density of dots of the image, the optical disk apparatus includes: a framing unit which makes a frame data by grouping a plurality of unit data, wherein when the dot data, the dot data are treated as the unit data; a pit forming unit which sequentially forms pits defined by a bit train signal of the frame data; a discrimination unit which determines whether the section in the frame data corresponding to the dot data is a predetermined value; and a gate unit which, in case the discrimination result by the discrimination unit is affirmative, supplies the bit train signal to the pit forming unit and, in case the discrimination result by the discrimination unit is negative, interrupts supply of the bit train signal to the pit forming unit.

BACKGROUND OF THE INVENTION

The present invention relates to an optical disk apparatus having afunction of recording data onto an optical disk as well as a function offorming an image.

Some of the optical disk apparatuss available in recent years have animage forming function of forming an image of a character or a figure inaddition to a recording function of recording data such as audio dataonto an optical disk including a CD-R (Compact Disc-Recordable) (forexample, refer to the Japanese Patent Laid-Open No. 7530/1996). Thistype of optical disk apparatus irradiates with laser light a recordingsurface on which data is recorded to change the color of part of therecording surface by means of heat, thereby forming an image of acharacter or a figure.

The image forming feature incorporated into an optical disk apparatusleads to a more complicated design of the optical disk apparatus, whichresults in an increase in device cost. A longer time required to form animage onto an optical disk or poor picture quality will impair the addedvalue.

SUMMARY OF THE INVENTION

The invention has been accomplished in view of such circumstances andaims at providing an optical disk apparatus capable of forming ahigh-quality image onto an optical disk at a high speed while preventingan increase in the device cost, and a program which supplies image datarequired by the optical disk apparatus.

In order to solve the aforesaid object, the invention is characterizedby having the following arrangement.

-   (1) An optical disk apparatus for forming an image on an optical    disk according to dot data which corresponds to intensity and period    of dots of the image, the optical disk apparatus comprising:    -   a framing unit which makes a frame data by grouping a plurality        of unit data, wherein when the dot data are applied to the        optical disk apparatus, the dot data are treated to be the        plurality of unit data;    -   a pit forming unit which sequentially forms pits defined by a        bit train signal of the frame data;    -   a discrimination unit which determines whether a section in the        frame data corresponding to the dot data is a predetermined        value; and    -   a gate unit which, in case the discrimination result by the        discrimination unit is affirmative, supplies the bit train        signal to the pit forming unit in a certain period of the dot        period and, in case the discrimination result by the        discrimination unit is negative, interrupts supply of the bit        train signal to the pit forming unit.-   (2) The optical disk apparatus according to (1), wherein the gate    unit supplies the bit train signal to the pit forming unit only in a    predetermined dot period required for formation of one dot in the    case the discrimination result is affirmative, and interrupts supply    of the bit train signal to the pit forming unit in the predetermined    dot period-   (3) The optical disk apparatus according to (2), wherein the framing    unit, when making the frame data by grouping the plurality of unit    data supplied from a host computer, adds parity data to correct a    code error of the plurality of unit data and synchronization data,    and    -   the optical disk apparatus further comprises time axis expander        unit which divides, by the number of dot data included in one        frame data, at least a period obtained by subtracting a period        of the synchronization data from a period in which the framed        data is output, and set the divided period as the predetermined        dot period.-   (4) An optical disk apparatus for forming an image on an optical    disk according to dot data which defines density of dots of the    image, the optical disk apparatus comprising:    -   a framing unit which makes a frame data by grouping a plurality        of unit data, wherein when the dot data are applied to the        optical disk apparatus, the dot data are treated as the        plurality of unit data;    -   a strategy circuit which corrects a bit train signal of the        frame data to form pits defined by the bit train signal on the        optical disk; and    -   a pit forming unit which applies laser light modulated by the        corrected bit train signal and sequentially forms pits onto the        optical disk;    -   wherein the strategy unit modifies the correction by the        strategy circuit so as to shorten or elongate a pit defined by        the bit train signal in accordance with an instruction from        outside.-   (5) A computer readable recording medium storing program which    causes a computer to which an optical disk apparatus is connected,    the optical disk apparatus comprising: a framing unit which    interleaves a plurality of unit data corresponding to dot data which    specifies density of a dot to be formed onto an optical disk in the    order the dot data are supplied and makes a frame data; and a pit    forming unit which forms a pit train according to the frame data so    that the density specified by the dot data to be processed will be    obtained, the program causing the computer to function as:    -   an acquisition unit which groups a plurality of dots positioned        on the same radius of an image defined in polar coordinates and        which acquires dot data defining the density of each of the        plurality of dots included in each group; and    -   a deinterleaving unit which rearranges the dot data acquired by        the acquisition unit and supplies the rearranged dot data to the        optical disk apparatus so that the arrangement of dot data after        the interleaving will match the arrangement of the dots in the        direction of an angle in polar coordinates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the entire system configurationincluding an optical disk apparatus according to a first embodiment ofthe invention;

FIG. 2 is a block diagram showing the configuration of the optical diskapparatus 100;

FIG. 3 is a block diagram showing the configuration of a write signalgenerator in the optical disk apparatus;

FIG. 4 shows the interleaving process in the optical disk apparatus;

FIG. 5 shows an EFM frame in the optical disk apparatus;

FIG. 6 is a timing chart showing the relationship between the rotationof the spindle motor and various signals;

FIGS. 7A and 7B illustrate the dots of an image to be formed onto anoptical disk.

FIG. 8 is a flowchart showing the operation of a host computer in imageformation;

FIGS. 9A to 9C show functional blocks of the host computer in imageformation;

FIG. 10 shows the deinterleaving process in the functional blocks;

FIG. 11 is a timing chart showing the image forming operation in theoptical disk apparatus;

FIG. 12 is a partial enlarged view of the optical disk which shows anexample of an image formed by the optical disk apparatus;

FIG. 13 is a block diagram showing the configuration of the write signalgenerator in the optical disk apparatus according to the secondembodiment of the invention;

FIG. 14 is a timing chart showing the image forming operation in theoptical disk apparatus; and

FIG. 15 illustrates the diffraction phenomenon in a hologram.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments according to the invention will be described referring tothe attached drawings.

<First Embodiment>

FIG. 1 is a block diagram showing the entire system configurationincluding an optical disk apparatus according to a first embodiment ofthe invention. As shown in FIG. 1, a system 1 comprises a host compute10 connected to an optical disk apparatus 100 according to thisembodiment. The host computer 100 comprises a CPU 20, a ROM 22, a RAM24, an HDD (Hard Disk Drive) 26, a display 28, an operating section 30,and an interface 32 interconnected to each other via a bus 21. The HDD26 stores an operating system as well as an application program forforming an image. The CPU 20 executes the application program toimplement functional blocks mentioned later and processes image data andsupplies the processed image data to the optical disk apparatus 100. Inthis embodiment, IDE (ATAP1) is used as a connection standard for theoptical disk apparatus 100. The operating section 30 includes a keyboardand a mouse which inputs an operation instruction from the user.

<Optical Disk Apparatus>

FIG. 2 is a block diagram showing the detailed configuration of theoptical disk apparatus 100. In FIG. 2, a main controller 120 controlseach section of the system and outputs various types of clock signals inaccordance with a program stored in the memory (not shown) providedtherein. The optical disk 200 is set so that its recording side willface a pickup 130 and is rotated by a spindle motor 136.

A rotation detector 138 generates for example eight pulses in a periodwhen the spindle motor 130 makes one turn and outputs the pulse signalas a detection signal FG. The optical disk apparatus 100 conforms to theCAV (Constant Angular Velocity) system in which the angular velocity isconstant. A spindle control circuit 140 performs feedback control of thespindle motor 136 under an instruction from the main controller 120 sothat the rotation speed indicated by the detection signal FG will beconstant.

Although details are omitted, generally speaking, the pickup 130integrates a semiconductor laser (oscillator) for emitting laser light,a photo-detector for detecting the intensity of the laser lightreflected onto the optical disk 200 (return light), a focus actuator fordriving an objective lens to gather the laser light in the directionapproaching or deviating from the optical disk 200, and a trackingactuator for operating the tracking of the laser light. The pickup 130is engaged with the rotation spindle of a stepping motor 144. Rotationof the spindle motor 144 is controlled by the main controller 120. Thepickup 130 is thus subject to feed control in the radius direction ofthe optical disk 200 by the main controller 120.

The semiconductor laser in the pickup 130 emits laser light at theintensity corresponding to a drive current supplied from the laserdriver 170. The return light of the laser light is converted to anelectric signal by the photo-detector. The electric signal is suppliedto a decoder 174, a power control circuit 178 and a pickup controlcircuit 180 respectively.

The interface (I/F) 152 connects to the host computer 10. In thisembodiment, the interface (I/F) 152 inputs recording data to be recordedin data recording while inputs image data processed as mentioned laterin image formation. A buffer 154 which is a first-in, first-out typetemporarily stores the data input from the interface 152. The data isread out in synchronization with the rotation of the optical disk 200detected by the main controller 120.

Although details are mentioned later, a write signal generator 156supplies to a laser driver 170 a signal OEN to indicate whether to applylaser light at a write level or a servo level in accordance with thedata read from the buffer 154. The write level refers to a levelsufficient for, when laser light at the level is applied to a recordinglayer (not shown) of the optical disk 200, the recording layer to bediscolored by heat to form pits. The servo level refers to the level atwhich the recording layer is not discolored by heat even when laserlight at the level is applied to the recording layer of the optical disk200. The servo level is used for focus control or tracking control.

The laser driver 170 generates a drive current which corresponds to thelevel specified by the signal OEN and which causes an error signalsupplied from the power control circuit 178 to become zero and suppliesthe drive current to the semiconductor laser of the pickup 130.

The power control circuit 178 detects the intensity of the return lightof the laser light actually applied by the semiconductor laser based onan electric signal from the photo-detector of the pickup 130 as well ascalculates the error between the actual intensity and the targetintensity to supply the error signal to the laser driver 170.

The target intensity of the laser light previously stored in the maincontroller 120 is read and supplied. Its value is an optimum valueobtained by way of recording and experiments. For the CAV system wherethe angular velocity is constant, the linear velocity increases as thelaser light approaches the edge of the optical disk 200. So that thepower control circuit 178 makes correction so that the target intensityat the write level will increase as the irradiation spot of laser lightmoves outward. In this way, the intensity of the laser light irradiatedfrom the pickup 130 is appropriately controlled in accordance with theirradiation position on the optical disk 200.

The pickup control circuit 180 generates a focus error signal and atracking error signal respectively by using a known technology on thebasis of an electric signal from the photo-detector in the pickup 130 aswell as drives the focus actuator in the direction where the focus errorsignal becomes zero and drives the tracking actuator in the directionwhere the tracking error signal becomes zero. In this way, the objectivelens is focus-controlled so that it will maintain a distance to thesurface of the optical disk 200 and focus on its recording surface, andtracking-controlled so that the focal spot of laser light will followthe track (pre-groove) of the optical disk 200.

<Write Signal Generator>

Next, the detailed configuration of the write signal generator 156 isdescribed referring to FIG. 3. The write signal generator 156 performsdata processing assuming 25-bit data as a single unit. One byte of the25-bit data is one added as a sub-code data D0. The remaining 24 bytesare main data to be recorded such as audio data. In this example, the 24bytes are called samples 1 through 24 in order for discriminating eachbyte.

An interleaver 1561 interleaves the samples 1 through 24 for example asshown in FIG. 4. In FIG. 4, for example sample 3 corresponds to maindata D7 after interleaving.

The interleaver 1561 adds parity data for correcting the errors ofsamples 1 through 24, four bytes between main data D12 and D13 and fourbytes immediately after main data D24. That is, immediately after maindata D12 is added parity data P1 through P4 and immediately after maindata D24 is added parity data Q1 through Q4, respectively.

An encoder 1562 then performs EFM (Eight to Fourteen Modulation) onone-byte sub-code data D0 and 24-byte main data D1 through D24 processedby the interleaver 1561 as well as parity data P1 through P4 and Q1through Q4 being eight bytes, total 33 bytes, to 16-bit data and framesthe 16-bit data in the format shown in FIG. 5

In the framing process, the encoder 1562 adds 24-bit synchronizationdata Dframe of a predetermined bit pattern at the beginning of a frameand inserts three merging bits between the (post-14-bit-conversion)sub-code data D0, main data D1 through 24, parity data P1 through P4 andQ1 Q4, respectively. As a result, one frame includes 588 bits.

Arrangement of the bits of frame data in chronological order is calledEFM data as shown in FIG. 5. When the bit “1” of the EFM data islevel-reversed in a waveform, the period when the EFM waveform (bittrain signal) is for example high defines a period (or length) when pitsare to be formed on the optical disk 200, and the period when the EFMwaveform is low defines the period of land as a pit space. On the EFMwaveform, a unit period corresponding to one bit is represented as IT.

Three merging bit shave four patterns; “000”, “100”, “010” and “001”(all binary notation). A pattern is chosen which satisfies theconditions that “0” between “1s” is consecutive within the range of 2through 10 0s even when the pattern is inserted between data items andthat, in case “+1” (decimal notation) is given when the EFM waveform ishigh and “−1” when it is low, the cumulative value per unit time (forexample 17T) is closest to “0”. Thus, the duration of the same level forthe EFM waveform is any of 3T through 11T and, as a result, the EFMwaveform has a duty ratio of about 50% for any portion extracted.

To the encoder 1562 is supplied various types of clock signals from themain controller 120 to execute framing. Of these clocks, a clock signalCLK is generated by a master clock and has a cycle of IT. A clock signal/EFMsync is driven low every 5888 cycles of the clock signal CLK. Thus,the encoder 1562 counts the clock signal CLK as well as resets the countresult by way of the fall of the clock signal /EFMsync therebyrecognizing the chronological position in a frame.

As shown in FIG. 6, the spindle control circuit 140 controls therotation of the spindle motor 136 so that the cycle of a signal xFBobtained by multiplying the frequency of a signal FG detected by therotation detector 138 will match the cycle of the clock signal /EFMsync.

Thus, the frequency-multiplied signal xFG corresponds to a period whenthe optical disk 200 rotates by a minute angle. The area correspondingto the minute angle on a track of the optical disk 200 (areacorresponding to a train in FIG. 6) becomes the one-frame storage area.

The strategy circuit 1563 corrects the EFM waveform and outputs theresulting waveform as a signal OENa. As mentioned above, the EFMwaveform defines pits (and land) to be formed on the optical disk 200.When the EFM waveform is driven high, applying laser light at the writelevel “as it is”, the pits formed do not match the EFM waveform. Thereason: even in case laser light is applied “as it is” when the EFMwaveform is driven high, the recording layer of the optical disk is notsufficiently heated, so that pits are formed in teardrops growing from athin shape to a thicker shape, or in case laser light is turned off “asit is” when the EFM waveform is driven low, the pits are deformed byelongation, in particular in the shape of a start posit and an endpoint, due to residual heat.

A signal Rec is supplied from the main controller 120 and instructs datarecording when it is driven high. The signal OENa is supplied to one ofthe input ends of a switch 1564 from the strategy circuit 1563. In casethe signal Rec is driven high and data recording is instructed, thesignal OENc is supplied as a signal OEN to the laser driver 170 (seeFIG. 1), along a solid line in FIG. 3. The signal OENa is a signalobtained by correcting the EFM waveform by the strategy circuit 1563, sothat laser light is applied in accordance with the signal modulated withthe EFM waveform. In case the signal Rec is driven low and imageformation is instructed, the switch 1564 follows the broken line in FIG.3 to supply as a signal OEN the signal OENb fed to the other input endto the laser driver 170.

For data recording, recording data supplied by the host computer 10 isstored in the buffer 154 then read as each item of main data D1 throughD24, byte by byte in order. Further, the data undergoes interleaving,incorporates parity data, and framed by the encoder 1562 to form pitsmatching the logical level of the EFM waveform on the optical disk 200.

For data regeneration, laser light is applied to pits and an electricsignal indicating its return light is supplied to the decoder 174 (seeFIG. 1) to obtain regenerated data. The decoder 174 detects theintensity of the return light base on the electric signal from thephoto-detector and detects the synchronization data Dframe from a changein the intensity. The decoder 174 then returns the data to 8-bit data byway of EFM demodulation and performs correction of an error if any, andexecutes deinterleaving opposite to FIG. 4 to obtain regenerated data.

In this embodiment, for ease of explanation, dot arrangement of an imageformed onto the optical disk 200 is described below referring to FIG.7A. As shown in FIG. 7A, on the optical disk 200, sectors are arrangedconcentrically from the first row to mth row, starting from the innerradius toward the outer radius, and per predetermined angle in radialdirection from the first column to the nth column clockwise on theoptical disk 200. Each sector has an area equally divided into 25sub-areas in the direction of perimeter, as shown in FIG. 7B. In thisembodiment, the one area corresponds to a dot of an image to be formed.Thus, in this embodiment, dots are arranged in a matrix of m rows by25·n columns. In this embodiment, these dots are represented in binaryform of white or black dots. As dot data representing white or block ofone dot, one byte (eight bits) is assigned. In case the dot data is“00000000” ($00 in hexadecimal notation), a white dot is specified. Incase the dot data is other than “00000000”, a black dot is specified.

Pits are not formed for white dots while pits are formed for black dotsand the reflectivity of the optical disk 200 is lowered to represent animage by means of the difference in the reflectivity. While only whiteor black dots are formed in this embodiment, the dot data is not one dotbut eight bits (one byte). As mentioned later, ore-dot data of onesector is supplied as a sub-code and the remaining 24-dot data issupplied as main data.

Thus, when such dot data is supplied to the write signal generator 156,the data is frames same as the data recording process. A configurationis required to discriminate the dot data as white dot or black dot aswell as form pits in accordance with the discrimination result. Theconfiguration will be described.

In FIG. 3, a discriminator 1565 determines whether the sub-code data D0and the 14 bits constituting the main data D1 through D24 are dataspecifying black dots. The data specifying black dots in the 14-bit dataafter conversion is data except “01001000100000”. The discriminator 1565determines whether black dots are specified depending on whether thesub-code data D0 and the each 14 bits constituting the main data D1through D24 are data except “01001000100000”.

Next, a time axis expander 1566 is a first-in, first-out buffer memoryand writes a valid discrimination result from the discriminator 1565 insynchronization with the slot for the EFM frame as well as reads thewritten discrimination result in synchronization with the clock signal/Dot to expand the data in the direction of time axis and rearranges thedata. The clock signal /Dot is a signal having the cycle (dot period) DTwhich is about one twenty-fifth the period obtained by subtracting theoutput period of the synchronization data Dframe and the merging bitsimmediately after Dframe from the period of one frame. The clock signal/Dot is supplied from the main controller 120.

A gate circuit 1567 causes the signal OENa from the strategy circuit1563 to pass in the period 24T (output period of the synchronizationdata Dframe) following the trailing edge of the synchronization signal/EFMsync. In the remaining period, the gate circuit 1567 gates thesignal OENa as described below. The gate circuit 1567 causes the signalOENa to pass in case the discrimination result of rearrangement is blackdot specification. The gate circuit 1567 interrupts the signal OENa incase the discrimination result of rearrangement is white dotspecification. The gate circuit 1567 supplies the signal obtained bygating the signal OENa to the other input end of the switch 1564. Thus,in case the signal Rec is driven low and image formation is instructed,the signal OENb from the gate circuit 1567 is supplied to the laserdriver 170.

<Image Forming Operation>

Next, operation of image formation in the system 1 will be described.When the user performs predetermined operation using the operatingsection of the host computer 10, the application program for imageforming stored in the HDD 26 is started. FIG. 8 is a flowchart showingthe procedure to execute this program.

The CPU 20 executes edit processing such as selection, editing andpositioning of an image (step Sa1). To be more precise, the CPU 20displays the outer shape of the optical disk 200 on the display 28 andlets the user select a target image, and displays a message instructingthe position on the optical disk on the screen for image formation. Theuser arranges the image on the optical disk by way of cut & paste orchanges the image by way of rotation and scale-down as required. The CPU20 repeats this edit processing until an image forming instruction isissued (step Sa2). In other words, an image forming instructiondetermines the image to be formed on the optical disk 200 and itsposition on the same.

Dots of image data are defined in the rectangular coordinate systemwhile dot arrangement on the optical disk 200 is defined in the polarcoordinate system, as shown in FIG. 7A. Thus, the CPU 20, receiving aninstruction of image formation, converts the image data in theRectangular coordinate system to data in the polar coordinate system andtemporarily stores the data into the RAM 24 (step Sa3). To be moreprecise, the CPU 20 determines which of the dots defined in therectangular coordinate system each of the dots arranged in m rows by 25n columns on the optical disk 200 belongs to, and determines whether thedata instructing the density of dots obtained specifies black dots ornot, and uses the determined data as dot data specifying the density ofdots in the polar coordinate system. As shown in FIG. 9A, assume thatthe origin of the Rectangular coordinates is set at the upper left andthe direction to the right and the direction to the bottom as positivedirection of X coordinate and positive direction of Y coordinaterespectively. When the center of an optical disk having the radius R ispositioned at Rectangular coordinates (R, R), the Rectangularcoordinates (x, y) (R+R·sin θ, R−r·cos θ) holds. The 25-dot data whichbelongs to one sector is stored into the RAM 24 in a matrix in rdistance and θ direction in the polar coordinates as shown in FIG. 9B.The CPU 20 specifies a white dot as “00000000” while it specifies ablack dot as any data randomly generated other than “00000000”.

Next, the CPU 20 sets ‘1’ to a variable i for identifying the targetsector row (step Sa4) and sets ‘i’ to a variable j for identifying thetarget sector column (step Sa5). The CPU 20 reads 25-dot data whichbelongs to the sector in the ith row and jth column (step Sa6). Thisacquires the 25-dot data which belongs to the sector identified by thevariables i, j at the present point in time. In case the processing ofstep Sa6 is executed for the first time, dot data of a sector in thefirst row and first column is read.

Further, as shown in FIG. 9C, the CPU 20 isolates the dot data whose θcomponent is the smallest out of the read dot data and supplies the dotdata as sub-code data to the optical disk apparatus 100 (see step Sa7 inFIG. 8). Meanwhile, the CPU 20 performs deinterleaving of dot data Db1through Db24 and supplies the resulting data to the optical diskapparatus 100 (see step Sa8 in FIG. 8). The contents of thedeinterleaving is reversal of the processing in the interleaver 1561 inthe optical disk apparatus 100 (see FIG. 4), as shown in FIG. 10.

When processing the 25-dot data which belong to one sector, the CPU 20determines whether the variable j is equal to n, the maximum value ofthe number of columns (step Sa9). In case the determination result isnegative, the CPU 20 increments the variable j by “1” in order to movethe target sector to next column (step Sa10) and returns to step Sa6. Incase the determination result is affirmative, the CPU 20 furtherdetermines whether the variable i is equal to m, the maximum value ofthe number of rows (step Sa11). In case the determination result in stepSa11 is negative, the CPU 20 increments the variable i by “1” in orderto move the target sector to next row (step Sal2) and returns to stepSa5. In case the determination result in step Sa11 is affirmative, thatmeans processing is over up to the final sector in the mth row and nthcolumn. The CPU 20 then terminates the program.

By the circulation of the steps Sa4 through Sal2, a sector to beprocessed shifts in the order of first row and first column, first rowand second column, . . . , first row and nth column, second row andfirst column, second row and second column, . . . , second row and nthcolumn, third row and first column, third row and second column, . . . ,third row and nth column, . . . , mth row and first column, mth row andsecond column, . . . , mth row and nth column. Dot data Db0 of the25-dot data which belongs to the sector to be processed is extracted assub-code data while the dot data Db1 through Db24 undergoesdeinterleaving and those data are supplied to the optical disk apparatus100.

Transfer of dot data to the optical disk apparatus 100 uses the RAW modein which data corresponding to 98 frames is transferred at a time as asingle block.

Next, operation of image formation in the optical disk apparatus 100will be described. Operation of each of the interleaver 1561, encoder1562 and strategy circuit 1563 is the same as that in data recordingexcept that data is dot data. Thus, dot data supplied from the hostcomputer 10 is stored into the buffer 155 and read in units of 25-doteach time the optical disk 200 turns by a minute angle corresponding toone column. Of the data, the dot data Db0 is directly supplied assub-code data D0 to the encoder 1562 while the dot data Db1 through Db24is supplied to the interleaver 1561. Note that, the dot data Db1 throughDb24 has been previously deinterleaved by the host computer 10, so thatwhen the data is interleaved by the interleaver 1561, the data isarranged in the order of sample in the EFM frame, as shown in FIG. 10.

The encoder 1562 isolates the dot data Db0 as sub-code data D0 as wellas frames the dot data Db1 through Db24 rearranged in the order of thesample as main data D1 through D24. In the framing process, thesynchronization data Dframe and the parity data P1 through P4 and Q1through Q4 are added, same as the data recording process. In datarecording also, any section of an EFM waveform has a duty ratio of about50% (see FIG. 5, FIG. 11).

As mentioned above, the discriminator 1565 determines whether each ofthe sub-code data D0 and the main data D1 through D4 14-bit-converted bythe encoder 1562 specifies black dots. The synchronization data Dframeand parity data P1 through P4 and Q1 through Q4 added in framing aremeaningless in image formation. Thus, the discriminator 1565 inputs theclock signal CLK and the synchronization signal /EFMsync to detect thechronological position in the frame, same as the encoder 1562. Thediscriminator 1565 outputs a signal representing that the abovediscrimination result is valid only in case the detected chronologicalposition is the output period of the sub-code data D0 and the main dataD1 through D24 and the above discrimination result is invalid in casethe position is the output period of the synchronization data Dframe andthe parity data P1 through P4 and Q1 through Q4. It is considered thatdiscrimination takes time on the discriminator 1565 so that the outputof the discriminator 1565 is output after a delay of one slot (17T).

The output result of the discriminator 1565 is shown in FIG. 11. Thestick in FIG. 11 indicates that the discrimination result of the 14-bitdata output in the slot period of the synchronization data Dframe andthe parity data P1 through P4 and Q1 through Q4 is invalid. Thus thevalid discrimination result is arranged unevenly over a single frame.The resulting data is temporarily written into the time axis expander1565 then read out in synchronization with the clock signal /Dot so thatthe slot period of the parity data P1 through P4 and Q1 through Q4 isshortened as shown in FIG. 11. As a result, the data is rearrangedalmost evenly over a single frame except the slot period of thesynchronization data Dframe.

When the discrimination result is white dot specification, the gatecircuit 1567 is closed over the period when the data is rearranged. Thuslaser light is applied at the servo level so that no pits are formed andthe reflectivity of the recording layer remains unchanged.

When the discrimination result is black dot specification, the gatecircuit 1567 is open over the period DT when the data is rearranged,that is, over the 100% period of the period DT. Thus laser light entersthe write level when the signal OENb output in the period is high, sothat pits are formed on the optical disk 200. The signal OENb is asignal corrected by the strategy circuit 1563 so that pits will beformed in accordance with the EFM waveform. Any section of the EFMwaveform irrespective of EFM data has a duty ratio of 50%. Thus theratio of the sum of the lengths of pits formed by way of thermochromismto the sum of the lengths of lands whose color has not changed is about50%. That is, the discrimination result output from the time axisexpander 1566 is rearranged so that the waveform section not related tothe EFM waveform as criteria for the discrimination result is extractedby the gate circuit 1567 to form pits in accordance with the waveformsection. When a waveform section not related to the discriminationresult is extracted to form pits in accordance with the waveformsection, the resulting ratio of pit to land is 1:1.

FIG. 12 is a partial enlarged view of the optical disk 200 on which pitsare formed, where the character “A” is displayed. Pits 202P are formedalong the pre-grooves 202G on the optical disk 200 by way of trackingcontrol. The ratio of the pits 202P to a single dot is a constant valueof about 50%. From a macroscopic viewpoint, black dots are of the samedensity.

According to the first embodiment, the configuration required to add theimage forming feature comprises the discriminator 1565, time axisexpander 1566, gate circuit 1567 and the switch 1654. This does notcomplicate the configuration of the optical disk apparatus 100 thuspreventing an increase in the device cost. The length of a sector in thedirection of perimeter is 163 μm when the linear velocity is a maximumof 1.2 m/second at the outermost perimeter. In this embodiment, 25 dotsin a sector are arranged in the direction of the perimeter so thatsufficient resolution is obtained. The length of a sector in thedirection of perimeter is 163 μm because 24-byte main data is stored inone frame, which data corresponds to six-sample audio data in twochannels of 16 bits and the sampling cycle is 44.1 kHz so that one cycleof one frame is 136 μsec.

Data stream in image formation is the same as that in data recordingexcept that the steam branches to the discriminator 1565, time axisexpander 1566 and the gate circuit 1567. Thus, the time required forimage formation is nearly the same as the time required for datarecording as long as the data amount is the same, without taking a longtime for image formation.

The gate circuit 1567 causes the signal OEN to pass in the period whenthe synchronization data Dframe is output, so that pits are formed onthe optical disk 200 in a pattern corresponding to the synchronizationdata Dframe. It is considered that this has little influence on thevisibility of an image formed on the optical disk 200. Thesynchronization data Dframe necessarily includes the write levelirradiation period so that it can be used for processing such as theabove-mentioned power control in the period. The synchronization dataDframe may be omitted same as the parity data P1 through P4 and Q1through Q4 in order to extend the period DT.

<Application of First Embodiment>

While dots are either white or black in the first embodiment,representation of halftones is made possible by adding the followingconfiguration. For example, in case 50% halftone (gray) is representedagainst black, the discriminator 1565 incorporates a feature todiscriminate dot data which specifies the gray. Alternatively, aseparate discriminator is added and in case the discrimination result isdot data which specifies gray, a configuration to reduce the gate periodto 50% the dot period DT is added. To be more precise, the signal OENbmay pass only in the period specified by the dot data out of the dotperiod DT. Similarly, support for a plurality of separate halftones willallow representation of multiple densities.

<Second Embodiment>

While it is possible to form an image onto an optical disk in the firstembodiment, the data recording configuration needed slight addition. Thesecond embodiment which requires little change in the hardwareconfiguration is described below.

FIG. 13 is a block diagram showing the configuration of the write signalgenerator 156 according to the second embodiment. As shown in FIG. 13,different from the configuration shown in FIG. 3, the second embodimentdoes not involve the discriminator l565, the time axis expander 1566,the gate circuit 1567 and the switch 1564. In the strategy circuit 1563a, correction in image formation is modified from the correction in datarecording by the instruction information WS from the main controller120. Other configuration of the second embodiment is the same as is inthe first embodiment.

In the second embodiment, in case dot data is $D2 (hexadecimalnotation), a white dot is specified. In case dot data is $82, a blackdot is specified. $D2 refers to “10001001001001” in terms of 14-bit dataafter conversion, and a pattern which makes level transition at thesection “/” of /4T/3T/3T/3T/ in terms of an EFM waveform. Similarly, $82refers to “10000100001001” in terms of 14-bit data after conversion, anda pattern which makes level transition at the section “/” of /5T/5T/3T/in terms of an EFM waveform. These two 14-bit data items start and endwith “1”. As merging bits inserted between these data items, only “000”satisfying two or more successive 0s between 1s out of the four patternsis selected.

When only $S2 and $82 are used as dot data Db0 through Db24, only thepattern 3T, 4T, 5T appears in the slot period from the sub-code data D0to the main data D12 and the slot period from the main data D13 to themain data D24, including merging bits.

The strategy circuit 1563 a, considering the appearance of this patternin image formation, corrects the EFM waveform in accordance with thefollowing rule and outputs the resulting waveform as a signal OENc.

That is, in image formation, in case the positive pulse width (Highlevel period) of the EFM waveform is 3T or 4T as shown in FIG. 14, thestrategy circuit 1563 a leaves 1T at the front edge and deletes 2T or 3Tat the rear edge. In case the positive pulse width is 5T, the strategycircuit 1563 a extends the High level period by 3T forward and backwardof the period to obtain 11T and outputs the pulse 11T as a signal OENc.

According to the second embodiment, when the signal OENc correspondingto white dot data is supplied to the laser driver 170, the pits 202Paccordingly formed are shortened with a small change in density as shownin FIG. 14. When the signal OENc corresponding to back dot data issupplied to the laser driver 170, the pits 202P accordingly formed arethick with a considerable decrease in reflectivity as shown in FIG. 14.This enhances the contrast ratio.

The parity data P1 through P4 and Q1 through Q4 is determined by thecontents of the dot data Db0 as sub-code data D0 and Dot data Db1through Db24 as the main data D1 through D24, and thus cannot beidentified. Correcting the patterns of 6T through 10T to make thinnerpits, same as 3T, 4T makes inconspicuous the pits formed in the slotperiod of the parity data P1 through P4 and Q1 through Q4, just likewhite dots.

In case a pattern whose positive pulse width is 5T accidentally occursas parity data, thick pits are formed by the pattern. The probability ofthis case to happen is not so high and the influence on the quality ofan image is rather small. Similarly, the probability of the patterns 6Tthrough 10T to happen is not so high. Thus, influence on the quality ofan image is rather small without the strategy circuit 1563 a correctingthe patterns 6T through 10T.

The pattern of 11T is used for processing such as power control by wayof the synchronization data Dframe, same as the first embodiment. Aconfiguration is also possible where the strategy circuit 1563 a doesnot correct the 11T pattern but makes correction so that the pits willbe shortened for 11T unless there is any specific application.

While white dots are specified when dot data is $D2 and black dots arespecified when dot data is $82 in the second embodiment, alternativedata may be used as long as the pattern used has 1s on both ends and 1salmost equidistantly.

While pits are shortened for white dots and elongated for black dots,the strategy circuit 1563 a may make correction in either case.

Thus, according to the second embodiment, it is possible to form ahigh-quality image on an optical disk in a relatively short time withoutadding hardware to a data recording configuration. Therefore, the deviceaccording to the second embodiment can be constructed by changing thesoftware (program) installed in a recording medium of the optical diskapparatus or a host computer controlling the optical disk apparatus.

<Application of Second Embodiment>

In the first embodiment, only a section of the EFM waveform is extractedand supplied to the laser driver 170 so that the pit shape is notdirectly related to dot data. It is thus impossible to define the pitinterval based on dot data. Meanwhile, according to the secondembodiment, pits are directly defined by way of a pattern obtained byconverting dot data to 14-bit data. It is thus possible to define thepit interval based on dot data.

When pits are formed at intervals which satisfy a condition, diffractionoccurs for the following reason. FIG. 15 is a cross-sectional view ofthe optical disk 200 along the direction of pits 202P-1, 202P-2. Asshown in FIG. 15, the pits 202P-1, 202P-2 are formed so that theinterval between the centers thereof will be equal to d. A visible lightimpinges in the direction of the normal to the optical disk 200. In casethe observer observes the recording surface of the optical disk 200 atan angle θ₁ to the direction of the normal, when the difference betweenthe optical path length from the pit 202P-1 to the observer and theoptical path length from the pit 202P-2 to the observer is a multiple ofan observed wavelength λ by an integer n, that is, whensin θ₁ =nλ/d  (1)is satisfied, the observed lights are in phase so that the lightsintensify each other, and the observer visually identifies the light ofthe wavelength as an intense light. In case the recording surface of theoptical disk 200 is observed at an angle θ₂, when the optical pathdifference between the pits 202P-1 and 202P-2 is a multiple of half anobserved wavelength λ by an odd number m, that is, whensin θ₂ =mλ/2d  (2)is satisfied, the observed lights 180 degrees out of phase so that thelights counteract each other, and the observer visually identifies thelight of the wavelength as a dim light.

In the second embodiment, when pits are formed at intervals d withappropriate dot data selected, the observer visually identifies thelight having the wavelength λ reflected against the pits as an intenselight when it is observed at an angle θ₁ and as a dim light whenobserved at an angle θ₂. It is thus possible to provide a formed imagewith a kind of hologram effect.

For the CAV system, the dot (pit) interval is elongated as theirradiation position moves from the inner radius toward the outer radiusof the optical disk 200. This must be considered in selecting anappropriate dot data (14-bit pattern).

While tracking control is used to form pits along the pre-grooves in thefirst and second embodiments, rotation of the optical disk 200 may besynchronized with the feed of the pickup 130 thereby forming an image.

While the first and second embodiments employ the CAV system in whichthe angular velocity is constant, the CLV (Constant Linear Velocity)system in which the linear velocity is constant may be used instead. Inthis case, it is necessary to consider that sectors are not aligned inradial direction in coordinate conversion. As the optical disk 200, aCR-R as well as various types of recording media such as a DVD can beused.

As mentioned hereinabove, according to the invention, it is possible toform a high-quality image onto an optical disk at a high speed withoutincreasing the device cost.

1. An optical disk apparatus for forming an image on an optical diskaccording to dot data which corresponds to intensity and period of dotsof the image, the optical disk apparatus comprising: a framing unitwhich makes a frame data by grouping a plurality of unit data, whereinwhen the dot data are applied to the optical disk apparatus, the dotdata are treated to be the plurality of unit data; a pit forming unitwhich sequentially forms pits defined by a bit train signal of the framedata; a discrimination unit which determines whether a section in theframe data corresponding to the dot data is a predetermined value; and agate unit which, in case the discrimination result by the discriminationunit is affirmative, supplies the bit train signal to the pit formingunit in a certain period of the dot period and, in case thediscrimination result by the discrimination unit is negative, interruptssupply of the bit train signal to the pit forming unit.
 2. The opticaldisk apparatus according to claim 1, wherein the gate unit supplies thebit train signal to the pit forming unit only in a predetermined dotperiod required for formation of one dot in the case the discriminationresult is affirmative, and interrupts supply of the bit train signal tothe pit forming unit in the predetermined dot period.
 3. The opticaldisk apparatus according to claim 2, wherein the framing unit, whenmaking the frame data by grouping the plurality of unit data suppliedfrom a host computer, adds parity data to correct a code error of theplurality of unit data and synchronization data, and the optical diskapparatus further comprises time axis expander unit which divides, bythe number of dot data included in one frame data, at least a periodobtained by subtracting a period of the synchronization data from aperiod in which the framed data is output, and set the divided period asthe predetermined dot period.
 4. An optical disk apparatus for formingan image on an optical disk according to dot data which defines densityof dots of the image, the optical disk apparatus comprising: a framingunit which makes a frame data by grouping a plurality of unit data,wherein when the dot data are applied to the optical disk apparatus, thedot data are treated as the plurality of unit data; a strategy circuitwhich corrects a bit train signal of the frame data to form pits definedby the bit train signal on the optical disk; and a pit forming unitwhich applies laser light modulated by the corrected bit train signaland sequentially forms pits onto the optical disk; wherein the strategyunit modifies the correction by the strategy circuit so as to shorten orelongate a pit defined by the bit train signal in accordance with aninstruction from outside.
 5. A computer readable recording mediumstoring program which causes a computer to which an optical diskapparatus is connected, the optical disk apparatus comprising: a framingunit which interleaves a plurality of unit data corresponding to dotdata which specifies density of a dot to be formed onto an optical diskin the order the dot data are supplied and makes a frame data; and a pitforming unit which forms a pit train according to the frame data so thatthe density specified by the dot data to be processed will be obtained,the program causing the computer to function as: an acquisition unitwhich groups a plurality of dots positioned on the same radius of animage defined in polar coordinates and which acquires dot data definingthe density of each of the plurality of dots included in each group; anda deinterleaving unit which rearranges the dot data acquired by theacquisition unit and supplies the rearranged dot data to the opticaldisk apparatus so that the arrangement of dot data after theinterleaving will match the arrangement of the dots in the direction ofan angle in polar coordinates.